Blotchy skin disorder rosacea finally explained

Researchers have solved a medical mystery that has eluded them for hundreds of years, demonstrating that an abundance of abnormal skin proteins causes the blotchy skin condition called rosacea.

In a study published Sunday in the online edition of the journal Nature Medicine, scientists showed that people with rosacea have too much of a protein called cathelicidin that is processed incorrectly.

The results could aid researchers in designing an effective treatment for the disease, which affects 14 million people in the United States.

Rosacea is a skin disease that causes redness, visible blood vessels, bumps and pimples on the face. It tends to strike more women, usually between ages 30 and 60, but men often have more severe symptoms.

"It's an appearance-related disease, so many people suffer from low self-esteem, and that can affect their everyday life," Kim said.

Options for treatment include light therapy to decrease redness, avoiding known triggers such as spicy foods and heat, and prescribing antibiotics that don't work for every patient.

About a dozen years ago, researchers in Gallo's lab discovered cathelicidin proteins, which help defend against infections in the skin. Gallo and his colleagues went on to find an association between the protein and skin conditions such as eczema.

The team later found that cathelicidin could cause the redness that is the hallmark of rosacea, so they started searching for a link.

The researchers took skin biopsies from 11 people with rosacea and 10 healthy people who served as controls. What they found was "a double hit of things going abnormally," Gallo said.

All the rosacea patients had too much cathelicidin, most of which was abnormal. There also was an abundance of a molecule that processes cathelicidin from an inactive to an active form. The way cathelicidin is processed is crucial to determining whether the protein will act as a defense against infection or promote inflammation, according to the study.

Experiments on mice confirmed the theory.

One of the most common treatments for rosacea is the antibiotic tetracycline. The study suggests that the drug is successful in rosacea patients because it inhibits cathelicidin processing, not because of its bacteria-killing properties. Future treatments might target the excessive production of cathelicidin's precursor, Gallo said.

To Dr. Jonathan Wilkin, head of the National Rosacea Society medical advisory board, "It's not that he's gone all the way back and discovered what the cause (of rosacea) is, but the role of cathelicidin in the engine that makes rosacea progressive, that is key."